A sweater knitted from a fibre that mimics polar bear fur offers as much warmth as a down jacket, despite being one-fifth as thick. The fibre — made from a light, synthetic material known as an aerogel — maintains its heat-trapping properties even after being stretched, washed and dyed.

A sweater knitted from a fibre that mimics polar bear fur offers as much warmth as a down jacket, despite being one-fifth as thick. The fibre — made from a light, synthetic material known as an aerogel — maintains its heat-trapping properties even after being stretched, washed and dyed.